I-BASE HIV TREATMENT BULLETINImportant note: Information in this article was accurate in November 2003. The state of the art may have changed since the publication date.
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Failure of alternating week-on and week-off therapy

HIV Treatment Bulletin - November 2003
Simon Collins, HIV i-Base


Two recently published studies, each based on different interruption protocols, have both shown disappointing results, with higher rates of treatment failure and development of resistance.

The rationale for these studies was that HAART-induced viral suppression could maintain viral benefit to allow short periods off treatment, with potential benefits of reduced toxicity and cost.

The first study, from NIAID, published in 1 August issue of Journal of Infectious Diseases, looked at the effect of long-cycle structured intermittent therapy (SIT). Treatment interrupted for four weeks followed by eight weeks with HAART was compared to continuous HAART. The study was prematurely terminated to new enrolment because of the emergence of genetic mutations associated with resistance to antiretroviral drugs in five patients. After 48 weeks, there was no significant difference between groups in reduced toxicity. There was also no clear autoimmunisation effect by immunologic or virologic parameters.

Results from the Staccato Study, published as a fast track article in the 17 October issue of AIDS, led to the early termination of one arm of this large international study in which 600 patients (from Thailand, Switzerland, Australia, Argentina and Australia) who were on stable HAART (viral load <50 copies/mL, CD4 >350 cells/mm3) were randomised 1:1:1 to either alternating one week on treatment with one week off, interrupting treatment and restarting by CD4 count or remaining on continuous treatment.

An interim analysis was performed after 150 patients had enroled which included 36 patients in the week-on week-off arm with 8-week data. Overall, 19/36 (53%) patients failed using this regimen. Early failures (within 12 weeks) included three out of four patients on triple nucleotides in Switzerland, and in 11 out of 17 patients on ddI/d4T/saquinavir/ritonavir in Thailand. ‘Late’ failures (after 12 weeks) included two patients on nelfinavir/3TC/AZT, one on saquinavir/ritonavir/d4T and one on nevirapine/3TC/AZT. Of eight patients on efavirenz/3TC/AZT, one has failed.

In the continuous treatment arm of the study, only two failures have occurred so far in 37 patients (P < 0.001, compared to the one-week-one-1-week-off). In the CD4-guided arm, no failures occurred in 39 patients. The week-on week-off arm of this study has now been terminated.

References:

  1. Dybul M, Nies-Kraske E, Daucher M et al. Long-cycle structured intermittent versus continuous highly active antiretroviral therapy for the treatment of chronic infection with human immunodeficiency virus: effects on drug toxicity and on immunologic and virologic parameters. J Infect Dis. 2003 Aug 1;188(3):388-96
  2. Ananworanich J, Nuesch R, Hirschel B et al. Failures of 1 week on, 1 week off antiretroviral therapies in a randomised trial. AIDS. 2003 Oct 17;17(15):F33-F37.

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